[CentOS-virt] [Advice] CentOS6 + KVM + bonding + bridging

Dennis Jacobfeuerborn dennisml at conversis.de
Thu Sep 6 12:28:27 EDT 2012

On 09/06/2012 06:19 PM, SilverTip257 wrote:
> With the current talk on bonding, I have a few questions of my own.
> I'm setting up a KVM host with CentOS 6.3 x86_64 on which I'd like to
> attach the VMs to a bonded interface.
> My target setup is one where two GigE NICs are bonded and then the KVM
> bridge interface is attached to the bonded interface.
> Initially I tried to use the balance-alb mode (mode6), but had little
> luck (receiving traffic on the bond appeared to be non-functional from
> the perspective of a VM).  After some reading [0] [1] - I switched the
> mode to balance-tlb (mode5) and hosts are now reachable.
> See bottom of [0] for a note on "known ARP problem for bridge on a
> bonded interface".
> I'd prefer mode5 or 6 since it would balance between my slave
> interfaces and need not worry about 802.3ad support (mode4) on the
> switch this host will be connected to.  But the way it seems mode 6
> isn't going to work out for me.  (Maybe experimenting with mode4 is
> the way to go.)
> [0] http://www.linux-kvm.org/page/HOWTO_BONDING
> [1] https://lists.linux-foundation.org/pipermail/bridge/2007-April/005376.html
> My question to the members of this list is what bonding mode(s) are
> you using for a high availability setup?
> I welcome any advice/tips/gotchas on bridging to a bonded interface.

You probably either want to use Centos 6.2 or wait for 6.4. Apparently
there have been some changes in the network device infrastructure with 6.3
kernels which resulted in bonding issues especially when used with vlan
tagging. I've been bitten by this and these issues have been addressed on
the red hat bugzilla but it's not entirely clear which kernel contains all
the final fixes.


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